Re: [Chicken-users] Chicken segfaults with large-ish inputs

[Nicolas Pelletier]

Hello,

On Sun, Feb 20, 2011 at 06:47, Sam Hardwick <address@hidden> wrote:
>
> (define (sum term a next b)
>  (if (> a b)
>      0
>      (+ (term a)
>         (sum term (next a) next b))))

You can use the following trick to accumulate intermediate results and
thus turn the call to sum into a tail recursive one:

(define (sum term a next b)
  (letrec ((helper (lambda (acc t a n b)
                     (if (> a b)
                         acc
                         (helper (+ acc (t a)) t (n a) n b)))))
    (helper 0 term a next b)))

With chicken 4.6.0, I get the following:

#;14> (integral cube 0 1 10)
0.25
#;15> (integral cube 0 1 100)
0.25
#;16> (integral cube 0 1 1000)
0.25
#;17> (integral cube 0 1 10000)
0.25
#;18> (integral cube 0 1 100000)
0.249999999999999
#;19> (integral cube 0 1 1000000) ; Used to crash from that point on
0.25
#;20> (integral cube 0 1 10000000)
0.25

Hope this helps,

-- 
Nicolas